My friend did truck bed lining spray in the back of his 944 and it is neat stuff. Buy a can of it and test it out on some piece of wood or metal and just see how thick it actually comes out. If you respay like 5 coats then its more like the rhino linex stuff. Try it out. There was a guy who posted a pic of a black painted plenum that wasnt sanded down to perfection smoothness but it was shiny due to the paint he used. Look for it n see if you like the way it looks rough and just pretend its not shiny.